Demonstration of a Nonlinear Angular Rate Sensor based on Internal Resonance

Abstract

This paper reports on the design, fabrication and rate table characterization of an H-shaped tuning fork microresonator with 2:1 internal resonance as an actuation mechanism. The nonlinear principle of operation addresses major challenges in MEMS Coriolis vibratory gyroscopes: eliminating the mode-matching requirement, minimizing instability and drift due to mechanical cross-coupling between the fundamental modes, and generating a wide operating frequency range with high-signal gain and less sensitivity to fluctuations in driving frequency. The rate measurement relies on capturing the half-order subharmonic response of the device while undergoing the angular velocity. The micromachined resonator is fabricated using the MEMS Integrated Design for Inertial Sensors platform offered by Teledyne DALSA Inc. The experimental finding demonstrated the prominent M-shaped nonlinear resonant curves due to a frequency ratio close to 2:1. The microresonator is nominally operated in the overlap region between the forward and backward frequency sweeps, where the signal gain is less sensitive to frequency fluctuations. The microresonator described here operates at 561.23600kHz in a near 2:1 frequency ratio between two anti-phase resonant modes. Experimental rate characterization of the microresonator revealed a linear dynamic range of 220 deg sec-1 with a sensitivity of 0.011 mV deg-1 sec-1 using an 80V DC polarization voltage. The experimental results of the microresonator showed the induced oscillations in the so-called pendulum mode by Coriolis force coupling, despite a clear disparity on natural frequencies of the desired modes.